It is 1972. Naomi Nakane, a thirty-six-year-old middle school teacher, recalls visiting a coulee, or ravine, in Granton, Alberta, with her uncle Isamu, her father’s half-brother, who she simply calls Uncle. They made the trip annually, beginning in 1954. The school year begins. Cecil, Alberta, where Naomi teaches, is a claustrophobically small town. Its inhabitants, predominantly white Canadians, are fascinated and a little mystified by Naomi. One day during class, she gets word that Uncle has died. She goes to see his widow, whom she calls Obasan (aunt in Japanese). A loaf of Uncle’s infamously inedible homemade bread sits on the counter. The two women go to the attic, where Obasan searches for something. Naomi thinks about her own mother’s unexplained disappearance some thirty years earlier.

Naomi and Obasan go to bed. Naomi dreams of two couples. One of the men is a British officer. She wakes to find that a package from Aunt Emily, her mother’s sister, has arrived. She reflects on Aunt Emily’s energetic crusades against racism, and for the remembrance and documentation of what happened to Japanese Canadians during World War II. Naomi begins thinking about her childhood, beginning with her family’s beloved house in Vancouver, and her favorite tale of Momotaro, a boy who emerged from a peach. She remembers releasing chicks into a cage with a hen that pecked many of the chicks to death. She remembers Old Man Gower, who repeatedly molested her beginning when she was four years old.

Naomi continues to think back on her past. In 1941, her mother went to Japan to see her own mother, who was ill. She never returned. Stephen, Naomi’s older brother, began to have trouble at school when other kids called him “Jap.” Grandma and Grandpa Nakane, her father’s parents, were imprisoned in Hastings Park, a holding area. Interrupting her memories, Naomi realizes that Stephen and Aunt Emily are on their way to the house.

She looks at one of the items in Aunt Emily’s package: a book of letters Emily wrote to her sister, Naomi’s mother. The letters chronicle the rapid deterioration of conditions for Japanese Canadians following the declaration of war. Their possessions were confiscated, and they were rounded up and sent to labor camps. Some families moved to ghost towns to escape persecution. During that time, Obasan took Naomi and Stephen to Slocan, an abandoned mining town, where they lived in a hut in the middle of the forest. For a time, they shared their living quarters with Nomura-obasan, an elderly woman. While in Slocan, Naomi’s paternal grandmother died. Grandma Nakane had been living in a town called New Denver after leaving an internment camp in Vancouver.

One winter day, Uncle joined them at the hut. Soon after his arrival, Stephen, whose leg had been in a cast for months, recovered. Summer came. One day, Naomi and her friend Kenji were playing by the lake when they encountered Rough Lock Bill, a local resident, who talked to them for a time. After he left, Naomi and Kenji took a raft onto the lake and drifted farther than they intended to go. Kenji abandoned Naomi in order to swim back to shore himself. She couldn’t swim but, afraid of drifting out too far, jumped into the water anyway. Rough Lock saved her from drowning. Naomi woke up in the hospital, where she thought about her father, who she knew was also in the hospital. She also thought about the racism her brother contended with, and the murder of innocent animals.

Germany surrendered. One night at the public baths, Naomi learned that Stephen and her father were sick with tuberculosis (TB). The morning after the war ended, Father came to the cabin. Soon after, the government ordered everyone out of Slocan. Father disappeared again.

Naomi returns to the present day. She recalls asking Aunt Emily what had happened to her mother and grandmother, and failing to get a response.

She remembers going with Obasan, Uncle, and Stephen to Granton in 1945. There they did backbreaking work on a beet farm owned by the Barkers, an ungenerous white family. Naomi’s family lived like animals in what had once been a chicken coop. Japanese Canadians were not allowed to return home until 1949. Naomi’s father died, a fact she didn’t allow herself to comprehend for some time. Stephen attended the Royal Conservatory of Music in Toronto, and went on to become a successful pianist. He rarely returned home, and when he did, he was surly.

Mr. Barker comes to Obasan’s house with his second wife to express his condolences for Uncle’s death. After the Barkers leave, Naomi sleeps and dreams of her mother. When she wakes, Aunt Emily and Stephen arrive along with Nakayama-sensei, an Anglican minister and old friend. He reads aloud some letters from Aunt Emily’s package. They are from Grandma Kato, Naomi’s mother’s mother, to her husband. They explain that Naomi’s mother never wanted her children to know what really happened to her in Japan. In 1945, Mother and Grandma Kato were caught in a bombing in Nagasaki. In that same bombing, Setsuko, Mother’s cousin and a new mother herself, was blinded and maimed. Setsuko’s son survived, but disappeared and was never found. Setsuko’s baby daughter got leukemia. In her attempt to save the children, Grandma was separated from Mother. A few days or weeks later, Grandma found Mother. She was alive, but horribly disfigured and plagued by maggots.

Naomi addresses her mother, who is dead now, and says she feels her presence. In the early morning, she drives to the coulee.